diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3
index a8151b24bf..38fe0ff40e 100644
--- a/docs/libcurl/curl_easy_setopt.3
+++ b/docs/libcurl/curl_easy_setopt.3
@@ -1388,6 +1388,7 @@ Resolve to ipv6 addresses.
 .IP CURLOPT_CONNECT_ONLY
 Pass a long. If the parameter equals 1, it tells the library to perform all
 the required proxy authentication and connection setup, but no data transfer.
+This option is useful only on HTTP URLs.
 
 This option is useful with the \fICURLINFO_LASTSOCKET\fP option to
 \fIcurl_easy_getinfo(3)\fP. The library can set up the connection and then the